This disclosure relates to a generator rotor and its rotor circuit.
A generator includes a stator fixed relative to a housing and a rotor rotatable about an axis relative to the stator. The rotor includes a rotor frame carrying a rotor circuit that includes field turns and a rectifier assembly, which has diodes. Rotation of the rotor relative to the exciter field (stator) induces an alternating current in the exciter armature (rotor) turns, which is converted to a DC voltage by the rectifier assembly.
Generators can experience rectifier assembly failures due to damaged diodes. One failure mode results from an electrostatic discharge event between the rotor frame and the isolated rotor circuit. The rotor circuit is electrically insulated from the rotor frame. The isolation of the rotor circuit can result in a build up of a high voltage potential on the rotor circuit relative to the rotor frame under common operational parameters. The voltage potential built up within the isolated rotor circuit discharges to the rotor frame when the voltage potential exceeds an insulation rating of the rotor frame. The voltage discharge can result in a voltage across the diodes in the rotor circuit that exceeds the diode voltage rating. This sudden voltage across the diodes results in a reverse bias on each diode. The reverse bias causes diode break down and shorting when the voltage exceeds the diode voltage rating, thus damaging the rectifier assembly.